This invention relates generally to an apparatus for a radiant wall burner assembly. More particularly, but in no way limiting, the present invention relates to a flow divider apparatus contained in a gas burner apparatus having a burner pipe.
Radiant wall burners have been previously disclosed in the prior art. These prior art burners typically include the use of a burner pipe which is usually inserted into an oversized opening through the wall of a furnace terminating at a downstream end perpendicular to and beyond the inner wall of the furnace. The inner wall of the furnace surrounding the furnace opening typically includes a radiant wall surface which is substantially perpendicular to the burner pipe. The downstream end of the burner pipe is typically closed by a cap, plug, or other device. A plurality of openings, such as slots or holes, are provided in the side wall of the burner pipe at the downstream end to project a fluid mixture, such as a gas/air mixture, outwardly along the radiant furnace wall surface for burning.
Fuel is introduced into the burner pipe around its centerline, while air is introduced at or near the pipe""s wall. While some mixing of the air and fuel occurs, due to the velocity of the gas/air mixture flow, the center portion of the flow stream remains fuel rich while the portion flowing near the furnace wall is fuel lean. When such a mixture combusts, the majority of the heat produced occurs away from the furnace wall, reducing effectiveness and efficiency of the furnace.
In order to assist the fluid flow from the burner pipe outward across the radiant wall, some prior art burners have utilized a flow divider which is inserted into the burner pipe. FIGS. 1-3 generally depict a typical prior art flow divider within a burner pipe. Unfortunately, however, the prior art flow dividers have not been able to adequately mix the fluid, especially around the centerline, into a uniform mixture prior to discharging into the furnace. These flow dividers continue to provide a fluid mixture which has a fuel rich center or downstream portion while having a fuel lean annular or upstream portion, as illustrated in FIG. 3.
U.S. Pat. No. 2,671,507, issued to Morck, which is incorporated herein by reference, discloses a radiant gas burner having a distributor for dividing the flow stream into a plurality of gas streams. The distributor utilizes a centralized plug and a plurality of fins to provide passages for the gas streams.
U.S. Pat. No. 4,702,691, issued to Ogden, which is incorporated herein by reference, discloses a radiant gas burner having a single cylindrical flow divider for dividing the flow stream into an upstream portion and a downstream portion. The flow divider creates a substantially undivided annular space between the burner pipe wall and the flow divider through which the upstream portion flows and an undivided inside central space within the flow divider through which the downstream portion flows. This device unfortunately does not provide for sufficient mixing of the fluid stream. Thus, the fluid stream remains primarily fuel rich along its downstream, or center, portion.
This invention is an improvement upon the radiant wall burning apparatuses heretofore developed. Specifically, the invention is directed to an improved flow divider for use in radiant wall burners.
The present invention provides a flow divider apparatus for a gas burner assembly which satisfies the needs and alleviate the problems discussed above. The inventive flow divider apparatus provides uniform flow velocities and also provides improved distribution of air or gas-air mixtures through the openings or slots provided in the end portion of the burner pipe.
A typical gas burner assembly in which the inventive flow divider apparatus is utilized can be employed, for example, in furnaces in which a high velocity fuel gas enters a burner pipe via an orifice to mix with combustion supporting air in a mixing section of the burner pipe. The burner pipe will typically be inserted into an oversized opening through the wall of the furnace such that the burner pipe is substantially perpendicular to, and the downstream end thereof extends beyond, the inner wall of the furnace. The inner wall of the furnace surrounding the furnace opening typically includes a radiant wall surface which is substantially perpendicular to the burner pipe. The downstream end of the burner pipe is typically closed by a cap, plug, or other device. A plurality of lateral side wall openings, such as slots or holes, are provided in the downstream end portion of the burner pipe to discharge the gas-air mixture outwardly along the radiant furnace wall surface for burning. Generally, the flow divider of the present invention is placed within the burner pipe near the downstream end thereof in order to divide the flow stream into a plurality of separate flow streams, each preferably being discharged at a different longitudinal location in the side wall of the burner pipe proximate to its distal end.
The present invention allows the fluid stream to mix more thoroughly due to turbulence caused by the impact of the fluid stream with the divided center section. This more thorough mixing of the fuel and air contained in the fluid stream allows for a more uniform and efficient distribution of fuel/air gases than previously provided by the prior art devices. As a result of the more uniform distribution of the fuel and air mixture, combustion is more balanced and a more even heat flux is provided.
In one aspect, the present invention involves a gas burner assembly for use in a furnace in which fluid flows therethrough. The assembly comprises: (a) a burner pipe through which fluids flow and (b) a flow divider comprising a plurality of nested members within said burner pipe defining an annular flow space between the side wall of the burner pipe and the outermost member, a core space within the innermost member, and at least one midstream space between the nested members. The burner pipe includes a plurality of openings or slots provided in the side wall of the burner pipe proximate to its distal (downstream) end.
As used herein, the term nested refers to the interfitting of two or more members. For example, when the number of nested members is two, there would be an outer member and an inner member. When the number of nested members is three, there would be an outer member, an inner member, and a midstream member located between the outer member and inner member.
The inventive flow divider is preferably positioned inside the burner pipe at the downstream end. The fluid stream is divided into a downstream portion which passes through the core space, an upstream portion which passes through the annular space, and at least one mid-stream portion which passes through at least one midstream space. The fluid stream then passes out the plurality of openings located in the burner pipe. The fluid which flows therethough can be, but is not limited to, a combination of pre-mixed fuel and aspirated combustion supporting air.
By way of example, when the flow divider of the present invention has two nested members, an annular flow space is formed between the side wall of the burner pipe and the outer member, a core space is formed within the inner member, and a midstream space is formed between the outer member and the inner member. When the number of nested members is three, an annular flow space is formed between the side wall of the burner pipe and the outermost member, a core space is formed within the innermost member, a first midstream space is formed between the outermost member and the middle member, and a second midstream space is formed between the middle member and the innermost member.
In another aspect of the inventive flow divider, the cross-section of each of the nested members is substantially cylindrical. It will, however, be understood by those skilled in the art that other geometric cross-sections could be utilized.
In another aspect of the inventive flow divider, each of the openings or slots around the downstream end portion of the burner pipe is divided into a downstream portion, an annular portion, and at least one midstream portion by flaring the downstream ends of the plurality of nested members such that they intersect and divide the openings in the side wall of the burner pipe. This flaring can be configured in a curved, tapered or beveled manner. Alternatively, a squared radial (i.e. substantially 90xc2x0) flaring perpendicular to the burner pipe openings can be used.
In yet another aspect, the flow divider of the present invention comprises a plurality of in-line members defining a plurality of flow sections. These plurality of in-line members preferably intersect along a longitudinally extending centerline or edge and generally extend radially from the centerline or edge toward the side wall of the burner pipe. The plurality of flow sections are defined by the spaces created between adjacent in-line members.
By way of example, when the number of in-line members is three, each extending from a common edge or centerline located substantially along the centerline of the burner pipe, a first flow section is created between the first in-line member, the second in-line member and the side wall, a second flow section is created between the second in-line member, the third in-line member and the side wall, and a third flow section is created between the third in-line member, the first in-line member and the side wall.
In yet another aspect, the present invention involves a gas burner assembly for use in a furnace in which fluid flows therethrough. The assembly comprises: (a) a burner pipe through which fluids flow and (b) a flow divider comprising a plurality of nested members within said burner pipe defining an annular flow space between the inside diameter of the burner pipe and the outermost nested member, a core space within the innermost nested member, and at least one midstream space between the nested members, and (c) a plurality of in-line members defining a plurality of flow sections, further dividing the annular space, the core space, and/or the midstream space(s), either individually or in combination. The burner pipe includes a plurality of openings or slots provided in the side wall of the burner pipe proximate to its distal (downstream) end.
By way of example, when the flow divider of this aspect of the present invention has two nested members and three in-line members, an annular flow space is formed between the side wall of the burner pipe and the outer member, a core space is formed within the inner member, and a midstream space is formed between the outer member and the inner member. The in-line members further divide the annular space, core space and/or midstream space into flow sections.
It is understood that the in-line members can divide the annular space, core space and midstream space either individually or in combination. By way of example, the in-line members may only be placed within the core space, thus dividing only the core space while not affecting the remaining flow spaces. By further example, the in-line members may only be placed within the core space and at least one midstream space, further dividing those spaces while not affecting the remaining spaces.
A better understanding of the present invention, its several aspects, and its advantages will become apparent to those skilled in the art from the following detailed description, taken in conjunction with the attached drawings, wherein there is shown and described the preferred embodiments of the invention, simply by way of illustration of the best mode contemplated for carrying out the invention.